Various kinds of recording media for recording digital data such as music contents and visual data are there, such as magnetic disks, optical disks, and magnetic optical disks. A semiconductor memory card, which is one type of such recording media, uses a semiconductor memory such as a flash ROM (Read Only Memory) as a recording element and makes it possible to reduce a size of a recording medium; therefore, semiconductor memory card is rapidly spreading with a focus on small size mobile apparatuses, such as digital still cameras and mobile telephone terminals.
Since data stored in a semiconductor memory card are managed by a file system, users can easily treat the stored data as a file. There is a FAT file system, used as a conventional file system, disclosed in ISO/IEC9293, “Information Technology-Volume and file structure of disk cartridges for information”, 1994. In addition, there are UDF (Universal Disk Format), NTFS (New Technology File System), and the like described in OSTA Universal Disk Format Specification Revision 1.50, 1997. The semiconductor memory card with data managed by such file systems can share a file between apparatuses that interpret the same file system; therefore, data can be given/received between apparatuses.
There has been a problem in that the file system needs to perform a two-stage operation in which data is first erased in rewriting data and thereafter data is written, resulting in much time consumed until finishing writing completely.
As a method for solving such a problem, for example, a semiconductor storage device disclosed in Japanese Unexamined Patent Publication No. 11-191297 is heretofore known. The present invention has a plurality of nonvolatile memories, performs erasing in a second nonvolatile memory when performing writing in a first nonvolatile memory, and performs rewriting data in a short time by processing them in parallel. However, in this conventional technology, the erase process is performed in parallel regardless of the data size to be written in a memory chip. For example, in a NAND type flash memory, time for erasing one erase block (normally, 16 KB) is to be 2.0 mSec. Accordingly, there has been a drawback in that it takes lots of time to perform erasing in the case of a small data size and, therefore, the entire writing time becomes longer after all.